Design assessment of non-safety level power supply to safety level instrument control system in molten salt reactor

The molten salt reactor designed by Shanghai Institute of Applied Physics, Chinese Academy of Sciences is a fourth-generation reactor with inherent safety. The design of the reactor has some features, for instance, the protection system is of safety level, while the power supply system that supplies it is of non-safety level. In order to evaluate the rationality of the design, based on the inherent safety characteristics of the reactor and the design characteristics of the protection system and its power system, the reliability of the AC power supply, the fault characteristics of the uninterruptible power supply, the power characteristics of the sensors that protect the system (including the nuclear measurement system), of the protection system, the electric features of the protection system cabinets and the shutdown circuit breaker cabinets, the manual driven characteristics and the consequences of the anticipated transient without scram (ATWS) are addressed. The assessment showed that the design meets the safety requirements and acceptability. For second-class research reactor, it is inappropriate to review the requirements of the auxiliary support system of the instrument control system of small nuclear power plants. The excessive requirements might bring non-significant safety benefits. (authors)